Characterization of advanced cyanate ester/epoxy insulation systems before and after reactor irradiation

Insulation systems for fusion magnets have to operate in a harsh environment, especially also under intense radiation. Over the past years, cyanate ester (CE) resins have been playing an increasingly important role because of their enhanced temperature and radiation resistance compared to conventional epoxy resins. Blending CE with epoxy resins offers the possibility to manufacture radiation resistant insulations at a low price compared to pure CE materials. Therefore, it is of special interest to study the influence of the CE content and of the epoxy resin on the mechanical properties to find materials, which are suitable and economically reasonable for the specific demands of such magnets.In this study R-glass fiber/Kapton reinforced cyanate ester/epoxy blends with different CE content were investigated. Each material was exposed to conditions matching those expected for the ITER TF coil insulation as closely as possible. In order to characterize the mechanical properties, short-beam shear and static tensile tests were carried out at 77 K prior to and after irradiation to fast neutron fluences of up to 5 × 10²² m⁻² (E > 0.1 MeV), in the TRIGA reactor (Vienna) at ambient temperature (340 K). In addition, tension-tension fatigue measurements were performed in the load-controlled mode to simulate the pulsed operation conditions of ITER.     

Characterization and qualification of advanced insulators for fusion magnets

Intensive research over the past decades demonstrated that the mechanical material performance of epoxy based glass fiber reinforced plastics, which are normally used by industry as insulating materials in magnet technology, degrades dramatically upon irradiation to fast neutron fluences above 1 × 10²² m^?2 (E > 0.1 MeV). which have to be expected in large fusion devices like ITER. This triggered an insulation development program based on cyanate ester (CE) and blends of CE and epoxies, which are not affected up to twice this fluence level, and therefore appropriate for large fusion magnets like the ITER TF coils. Together with several suppliers resin mixtures with very low viscosity over many hours were developed, which renders them suitable for the impregnation of very large volumes. This paper reports on a qualification program carried out during the past few years to characterize suitable materials, i.e. various boron-free R-glass fiber reinforcements interleaved with polyimide foils embedded in CE/epoxy blends containing 40% of CE, a repair resin, a conductor insulation, and various polyimide/glass fiber bonded tapes. The mechanical properties were assessed at 77 K in tension and in the interlaminar shear mode under static and dynamic load conditions prior to and after reactor irradiation at ~340 K to neutron fluences of up to 2 × 10²² m^?2 (E > 0.1 MeV). i.e. twice the ITER design fluence. The results confirmed that a sustainable solution has become available for this critical magnet component of ITER.     

Processing characteristic and radiation resistance of various epoxy insulation materials for superconducting magnets

Glass fiber reinforced epoxy-based composites were developed as insulating materials for fusion superconducting magnets. The processing properties of various epoxy matrices were investigated in terms of the isothermal viscosity at 45 °C. The interlaminar shear strength (ILSS) at 77 K and the thermal expansion coefficient (CTE) of the composites were assessed before and after gamma irradiation at ambient temperature up to 10 MGy. It is found that the TGPAP-based systems showed lower initial viscosities, longer working life and higher radiation resistance compared to the DGEBF-based systems with the same modifier. Furthermore, there was no significant effect of the irradiation dose on the CTE of the composites.     

尼龙66/紫外辐照线性低密度聚乙烯共混物的力学性能

通过紫外辐照实现了高密度聚乙烯(HDPE)的官能化，改善了HDPE复合材料的性能。本工作采用傅立叶红外(FT-IR)、X射线光电子能谱(XPS)、凝胶、熔融指数和水接触角测试等研究了紫外辐照对线性低密度聚乙烯(LLDPE)化学结构和性能的影响。紫外辐照后，在LLDPE的分子链上引入了C=O、C-O和C(=O)O等含氧基团，其含量随辐照时间延长而增加。凝胶分析结果表明，紫外辐照过程中，LLDPE产生凝胶，     

一种Zr基非晶/晶体复合型核材料的力学性能与耐腐蚀性能的研究

采用Zr65Cu35和Nb双靶直流共溅射方法,通过调节Nb靶的溅射功率,制备了不同Nb含量的Zr Cu Nb非晶薄膜。分别使用能谱仪、X射线衍射仪、高分辨透射电子显微镜观察Zr Cu Nb非晶薄膜的成分与结构,最终选择具有优异非晶形成能力的Zr53Cu38Nb9成分溅射到纯Zr基片上,以制备锆基非晶复合材料。研究测试Zr53Cu38Nb9非晶复合材料的力学性能与耐腐蚀性能。结果表明:与纯Zr基片相比,复合材料在弹性阶段力学性能无明显差异;而在塑性变形阶段,由于非晶薄膜与纯Zr基片的变形与断裂机制不同,该复合材料具有更好的拉伸塑性,其表现为非晶膜厚为280 nm、640 nm和960 nm的复合材料的最大拉伸塑性形变较纯Zr基片分别提高了2.72%、5.22%、4.27%;在耐腐蚀性能方面,非晶膜厚为640 nm的复合材料与纯Zr基片相比,具有较小的自腐蚀电流密度icorr、较正的腐蚀电位Ecorr以及较大的容抗弧半径,表现出更优异的耐腐蚀能力。因此,该新型Zr基复合材料在核材料领域具有潜在的应用。     

Studies on mechanical, thermal and morphological properties of irradiated recycled polyamide and waste rubber powder blends

The aim of this article was to show the effect of gamma irradiation on mechanical and thermal properties of recycled polyamide (rPA) copolymer blended with different content of waste rubber powder (WRP). In order to study the structural modifications of prepared blends have been subjected to irradiation doses up to 200 kGy were applied to all samples. Non-irradiated blends were used as control samples. Mechanical properties, namely, tensile strength (TS), elastic modulus, elongation at break and hardness have been followed up as a function of irradiation dose and degree of loading with rubber content. Furthermore, the influence of radiation dose in the thermal parameters, melting temperature, heat of fusion, ΔH_f of the recycled PA and its blend with waste rubber powder (WRP) was also investigated.     

Effect of electron beam radiation on the polypropylene/polyethylene blends: Radiation stabilization of polypropylene

The effect of incorporation of polyethylene in the polypropylene matrix, on the radiation sensitivity of polypropylene, has been investigated. The changes in the properties such as tensile strength, elongation at break, Shore D hardness, density and melt flow index were monitored as function of polyethylene content and electron beam radiation dose. A correlation between the mechanical properties and morphology of the irradiated polymeric blends has been observed, which has been explained on the basis of Fourier-transform infrared spectroscopy, scanning electron microscope and X-ray diffraction studies. Improvement in the mechanical properties of the polypropylene, irradiated to an optimum electron beam dose, could be achieved by blending it with polyethylene >20%. The optimum radiation dose was found to be dependent on blend composition and morphology, however, an absorbed dose of 250 kGy found to be effective enough to ensure good mechanical properties of the polypropylene/polyethylene blends.     

辐照交联对膨胀阻燃剂/乙烯-辛烯共聚物复合材料力学性能及阻燃绝缘性能的影响

采用机械共混法向乙烯-辛烯共聚物中添加不同含量的膨胀阻燃剂(聚磷酸铵、季戊四醇、三聚氰胺),然后采用电子束辐照,制备出交联型膨胀阻燃复合材料。通过极限氧指数、热失重、燃烧性能等参数表征电子束辐照交联对其阻燃性能的影响。结果表明,辐照交联后,复合材料的氧指数提高1~2;对力学性能而言,断裂伸长率随着吸收剂量的增加呈现下降趋势,拉伸强度则呈现上升趋势;对热释放的影响,复合材料的燃烧过程缩短,释热、释烟更为集中,在200 kGy吸收剂量下辐射交联后,总热释放量由94.8 MJ/m~2下降至79.1 MJ/m~2,总烟释放量由1 122.9 m~2/m~2下降至928.4 m~2/m~2,燃烧过程缩短约25%,CO释放率由0.062 2kg/kg下降至0.043 9 kg/kg,CO_2生成率由1.44 kg/kg上升至1.51 kg/kg;对绝缘性能而言,随着吸收剂量的增加,材料的体积电阻率变化幅度很小,提示辐照对材料的绝缘性能影响很小。     

Study on thermal and mechanical properties of cis- and trans-polyisoprene blends implanted by carbon ions

In the present work, elastomeric blends of cis- and trans-polyisoprene prepared by solution casting have been implanted by carbon ions (C⁶⁺) at three different fluencies with 87 MeV energy. The implanted samples were characterized through X-ray diffraction. The thermal transport and mechanical properties of implanted samples have been investigated using transient plane source and dynamic mechanical analyzer respectively. It was found that both thermal transport and mechanical properties show increasing trend up to certain fluence and beyond this fluence a decrease is observed. The variations in these properties have been discussed in terms of crosslink density and crystallinity.     

辐射灭菌对壳聚糖管力学性能和生物降解性的影响研究

采用剂量为25kGy的γ射线对壳聚糖管进行辐射灭菌,并测试了其体外降解性能、溶胀性能和力学性能。结果表明,γ射线辐射灭菌明显降低了溶菌酶对壳聚糖管的降解速率和其在水溶液中的溶胀,并显著提高了其拉伸强度和弹性模量。同时,运用傅里叶红外光谱(FTIR)、X射线衍射(XRD)和差热分析(DSC)表征了辐射灭菌前后壳聚糖材料的化学结构和结晶形态,探讨了辐射灭菌对壳聚糖管性能影响的机制。     

辐射硫化对三元乙丙橡胶力学性能的影响

以三元乙丙橡胶(Ethylene propylene dine terpolymer rubber,EPDM)为基材,三羟甲基丙烷三甲基丙烯酸酯(Trimethylopropane trimethylacrylate,TMPTMA)为交联敏化剂,采用60Co对其进行辐射硫化。研究了不同吸收剂量、不同TMPTMA用量对EPDM的凝胶分数和力学性能的影响,并通过热空气老化测试和热重分析,研究了辐射硫化橡胶与化学硫化橡胶耐老化性和热稳定性。结果表明:随着TMPTMA用量的增加,EPDM的凝胶分数增加,适宜用量为EPDM质量的8%。吸收剂量在120 kGy以下时,拉伸强度、伸长率为100%时的弹性模量及邵氏A硬度随着剂量的增加而增加,而断裂伸长率减小,合适的吸收剂量为约80 kGy。热空气老化后,化学硫化橡胶的拉伸强度及断裂伸长率迅速下降,而辐射硫化橡胶的拉伸强度先增加后减小,断裂伸长率缓慢降低。热重分析结果显示,化学交联的EPDM在430℃-480℃发生热分解,辐射硫化交联的EPDM的热分解温度为480℃-530℃。这些结果表明辐射硫化橡胶比化学硫化橡胶的耐老化性能和热稳定性好。     

耐温屏蔽复合材料的研制及性能研究

为满足核电站、乏燃料存储设施等对防护材料的耐温性、热稳定性、耐辐照性能等要求,研制四官能环氧树脂基(AGA型)耐温屏蔽复合材料。首先对基体材料的热稳定性进行分析,由热重分析(thermogravimetric analysis,TG)曲线得到其起始分解温度为353.5℃,200℃恒温储存170 h后,基体材料失重1.22%。动态热机械性能分析(dynamic thermomechanical analysis,DMA)表明,随着钨(W)含量的增加,AGA型耐温屏蔽复合材料的玻璃化温度向高温区移动并且峰型变宽。用⁶⁰Co放射源辐照50 kGy剂量,当AGA型耐温屏蔽复合材料的W含量10.5 wt%,B₄C含量3 wt%时,其辐照前后冲击强度均为最优。用²⁵²Cf中子源测试2 cm厚AGA型耐温屏蔽复合材料的屏蔽性能,当加入3 wt%的B₄C时,AGA-4耐温屏蔽复合材料的快中子透射率为50.00%。实验结果表明,AGA型耐温屏蔽复合材料具有一定的耐温性和耐辐照性能,并且密度较小。     

Mechanical properties of unidirectional and crossply SiCf/SiC composites using SiC fibers with carbon interphase formed by electrophoretic deposition process

Unidirectional (UD) and crossply (CP) SiC_f/SiC composites with different fiber volume fraction were fabricated based on EPD and sheet stacking process, and their mechanical properties were evaluated at room temperature. The UD-SiC_f/SiC composites showed a pseudo-ductile fracture behavior in bending test. Bending strength and fracture energy of the UD-SiC_f/SiC composites with high V_f (66%) was higher than those of the UD-SiC_f/SiC composites with low V_f (47%). Although the CP-SiC_f/SiC composites also fractured in a non-brittle manner, their bending strength and fracture energy were much lower than the UD-SiC_f/SiC composites because the SiC fibers aligned in 90° direction did not work for toughening and strengthening the SiC_f/SiC composites. In the UD-SiC_f/SiC composites, fiber pullout was clearly observed, and the number of fiber pullout in the UD-SiC_f/SiC composites with high V_f was large rather than the UD-SiC_f/SiC composites with low V_f. On the other hand, fiber pullout did not appear in the CP-SiC_f/SiC composites with low V_f whereas large number of fiber pullout was observed in the CP-SiC_f/SiC composites with high V_f. This can be explained by the thickness of the SiC matrix-layers between SiC fiber-layers.     

辐照对高分子磁体/M型铁氧体复合物电磁性能的影响

报道了在^60Coγ辐照下二茂铁高分子磁体／M型六角晶系铁氧体复合物(简称OPM／M型)辐照剂量、组分配比、温度对复合物电磁参数的影响,并用IR差示光谱、SEM(电子扫描显微镜)研究了辐照剂量对复合物的降解与交联之影响。研究表明,适当的辐照剂量及组分配比可控制复合物的电磁参数,并有可能获得一种用于0．1—12GHz下的轻质和良好吸波特性的新型吸波剂。     

Effects of ion irradiation on the mechanical properties of SiNawOxCyHz sol-gel derived thin films

A study of the effects of ion irradiation of hybrid organic/inorganic modified silicate thin films on their mechanical properties is presented. NaOH catalyzed SiNa_wO_xC_yH_z thin films were synthesized by sol-gel processing from tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) precursors and spin-coated onto Si substrates. After drying at 300 °C, the films were irradiated with 125 keV H⁺ or 250 keV N²⁺ at fluences ranging from 1 × 10¹⁴ to 2.5 × 10¹⁶ ions/cm². Nanoindentation was used to characterize the films. Changes in hardness and reduced elastic modulus were examined as a function of ion fluence and irradiating species. The resulting increases in hardness and reduced elastic modulus are compared to similarly processed acid catalyzed silicate thin films.     

A study on the electric properties of single-junction GaAs solar cells under the combined radiation of low-energy protons and electrons

Displacement damage induced by charged particle radiation is the main cause of degradation of orbital-service solar cells, while the radiation-induced ionization shows no permanent damage effect on their electrical properties. It is reported that in single crystal silicon solar cells, low-energy electron radiation does not exert permanent degradation of their properties, but the fluence of electron radiation exerts an influence on the damage magnitude under the combined radiation of protons and electrons. The electrical properties of the single-junction GaAs/Ge solar cells were investigated after irradiation by sequential and synchronous electron and proton beams. Low-energy electron radiation showed no effects on the change of the solar cell properties during sequential or synchronous irradiation, implying ionization during particle radiation could not exert influence on the displacement damage process to the solar cells under the experimental conditions.     

The effect of the electron irradiation on the series resistance of Au/Ni/6H-SiC and Au/Ni/4H-SiC Schottky contacts

The effect of electron irradiation on Au/Ni/6H-SiC and Au/Ni/4H-SiC Schottky contacts has been studied by current voltage (I-V) characterization at room temperature. The diodes have been subjected to the electron irradiation at various energies (6, 12 and 15 MeV) and influence of the electron irradiation on the diode parameters such as barrier height, ideality factor, and series resistance has been studied. Cheung functions, Norde model and conductance method have been used to determine the diode parameters. The ideality factor of the diodes is greater than unity indicating activation of some other current transport mechanism(s). The series resistances of the diodes increase by increasing electron energy. The reverse current increases for the Au/Ni/6H-SiC diode after each electron irradiation experiment, while decreasing trend is observed for Au/Ni/4H-SiC diode. Decrease in the barrier height of Au/Ni/4H-SiC diode is observed and mainly attributed to the increase of the reverse current, while the decrease of the forward current is caused by increase in series resistance, for high electron irradiation energies.     

辐射和热同时作用对膨润土物理化学性质和微观结构影响的初步研究北大核心CSCD

为了研究γ辐射和热同时作用对膨润土的影响,以高庙子改性钠基膨润土为研究对象,开展了90℃热作用下、不同剂量率和不同累积剂量的γ辐射老化试验。结果表明:γ辐射和90℃热同时作用引起了膨润土物理化学性质和微观结构的变化。在老化作用后,膨润土的吸水率、pH值、阳离子交换容量、层荷以及蒙脱石001晶面方向的微晶尺寸均减小,比参考样分别降低了(最大减幅)18.4%、7.8%、3.4%、2.9%和15.6%,且表现出剂量率效应;老化作用对膨润土的矿物成分及含量影响较小。在高放废物地质处置的工程屏障设计和安全评价中,应考虑膨润土性质变化的影响因素。     

Effect of mechanical properties in the weld zone on the structural analysis results of a plate-type heat exchanger prototype and pressurized water reactor spacer grid

The mechanical properties in a weld zone are different from those in the base material owing to their different microstructures. A process heat exchanger in a nuclear hydrogen system is a key component to transfer high heat generated in a very high-temperature reactor to a chemical reaction that yields a large quantity of hydrogen. A spacer grid in pressurized water reactor (PWR) fuel is a structural component with an interconnected and welded array of slotted grid straps. Previous research on the strength analyses of these components was performed using base material properties owing to a lack of mechanical properties in the weld zone. In this study, based on the mechanical properties in the weld zone of components recently obtained using an instrumented indentation technique, strength analyses considering the mechanical properties in the weld zone were performed, and the analysis results are compared with previous research.     

Influence of annealing temperatures and time on the photoluminescence properties of Si nanocrystals embedded in SiO2

We report on the effects of annealing conditions on the photoluminescence from Si nanocrystal composites fabricated by implantation of Si ions into a SiO₂ matrix, followed by thermal treatment in a nitrogen atmosphere. The evolution of the photoluminescence under different annealing temperatures (900–1100 °C) and annealing time (0.5 up to 5 h) were systematically studied for the implanted samples. After annealing the spectra presented two photoluminescence bands: one centered at 610 nm and another around 800 nm. Combined with transmission electron microscopy, we conclude that the photoluminescence behavior of the two bands suggests different origins for their emissions. The 610 nm band has its origin related to matrix defects, while the 800 nm band can be explained by a model involving recombination via quantum confinement effects of excitons in the Si nanocrystals and the interfacial states recombination process confined in the interfacial region between nanocrystals and SiO₂ matrix.